As is well known, the flow of sand and similar fine materials into a wellbore, such as an oil well or the like, can virtually halt production from the well in a relatively short period of time. Heretofore, various techniques have been used to control the flow of sand into a wellbore. For example, techniques exist for constructing wire mesh cages, screens, slotted liners, gravel packs, formation consolidations and gravel consolidations within a wellbore which in turn retain one or more layers of fill material. In this manner the flow of production fluids into the wellbore is permitted, but sand and other fine materials are prevented from entering the well.
Another known technique for effecting sand control in oil wells and similar wellbores involves the use of commercially available fluid resin materials. Heretofore, the fluid resin materials have been dispersed into the formation perforations within the wellbore by means of hydraulic pressure. The resin materials subsequently polymerize to retain sand and similar fine materials while permitting the flow of production fluids into the well.
It has been found that the hydraulic pressurization technique requires the use of substantial quantities of fluid resin material in order to effect sand control in a typical wellbore. It is theorized that because the hydraulic pressurization technique applies a relatively low pressure over a relatively long period of time, the fluid resin material is allowed to follow paths of least resistance. These relatively open fluid flow paths must be substantially filled with the fluid resin material before other, more restrictive flow paths receive a sufficient quantity of the fluid resin material to effect sand control. Indeed, in many instances the fluid resin material does not reach all the perforations.
Commercially available fluid resin materials used to effect sand control in wells are quite expensive, thus, any excess usage of the fluid resin materials raises the cost of well treatment significantly. In many instances the material costs associated with prior art fluid resin sand control techniques are so high that the use thereof is negated in marginally productive wells.
In accordance with the present invention, a gas generator is utilized to disperse a fluid resin material within the formation perforations in order to effect sand control in the well. More specifically, a quantity of fluid resin material is placed within the wellbore in alignment with the formation perforations and a gas generator is positioned in proximity with the quantity of fluid resin material. Subsequently, the gas generator is actuated to disperse the fluid resin material within the formation perforations in accordance with a pressure/time relationship. It has been found that the use of the present invention requires substantially less fluid resin material to effect sand control than is required when the prior art hydraulic pressurization technique is employed. Thus, the material costs involved in the use of fluid resin materials to effect sand control is substantially reduced when the present invention is employed. Additionally, the present invention increases well productivity and is less damaging to the permeability of the formation. More importantly, the present method results in greater sand control.
Some commercially available fluid resin materials, including externally catalyzed resins such as furan and phenolic resins, that are utilized for sand control in oil wells and the like, require the use of acid to polymerize the resin materials. Other commercially available fluid resin materials, including internally catalyzed resins such as epoxy resins, polymerize at a slower rate in the presence of acid and may require the use of a flush solution such as oil or brine to restore the permeability of the formation.
It has been found that the products of combustion resulting from the use of the gas generator may be sufficiently acidic to polymerize the resin without the necessity of introducing acid into the well for polymerizing the fluid resin material. In those instances the use of the present invention further reduces material costs by eliminating the necessity of using acid to polymerize the resin material.
In some embodiments utilizing externally catalyzed fluid resins the addition of acid aids in the polymerization of the fluid resin material and, consequently increases sand control. In some embodiments utilizing internally catalyzed resins, the presence of acid inhibits the polymerization of the fluid resin and may be used to delay polymerization.
Although primarily directed to fluid resin type sand control techniques, the present invention may also be utilized to apply other fluids, such as chemicals for controlling sand, water, clay, scale, corrosion, oxidation emulsions, paraffin or pH for well treatment to selected regions of a wellbore. Thus, in accordance with the broader aspects of the invention, a selected fluid is aligned within a predetermined region of a wellbore. Thereafter, a gas generator is positioned in proximity with the fluid and actuated to force the fluid resin material into the selected region of the wellbore in accordance with a pressure/time relationship. In this manner, the selected region of the wellbore is treated with the fluid in a substantially instantaneous but controlled manner in order to treat substantially all portions of the selected region of the wellbore in an identical manner while requiring a minimum amount of fluid.
Thus, the present invention provides numerous advantages over the prior techniques, while eliminating deficiencies therein.